1. Field of the Invention
This invention relates to surgical stapling instruments, and more particularly, to a graduated anvil for surgical stapling instruments configured to sequentially apply a plurality of surgical fasteners to body tissue and optionally incise the fastened tissue.
2. Description of Related Art
Surgical stapling devices wherein tissue is first grasped or clamped between opposing jaw structure and then joined by means of surgical fasteners are well known in the art. In some instruments a knife is provided to cut the tissue which has been joined by the fasteners. The fasteners are typically in the form of surgical staples or two part polymeric fasteners.
Instruments for this purpose can comprise two elongated members which are respectively used to capture or clamp tissue. Typically, one of the members carries a disposable cartridge which houses a plurality of staples arranged in at least two lateral rows while the other member comprises an anvil which defines a surface for forming the staple legs as the fasteners are driven from the cartridge. Generally, the stapling operation is effected by a pusher which travels longitudinally through the cartridge carrying member, with the pusher acting upon the staples to sequentially eject them from the cartridge. A knife may be associated with the pusher between the staple rows to longitudinally cut and/or open the tissue disposed between the rows of staples. Such instruments are disclosed, for example, in commonly assigned U.S. Pat. Nos. 3,079,606, 3,490,675 and 5,014,899.
A later stapler disclosed in U.S. Pat. No. 3,499,591 to Green applies a double row of staples on each side of the incision. This is accomplished by providing a cartridge assembly in which a cam member moves through an elongate guide path between two sets of staggered staple carrying grooves. Staple drive members are located within the grooves and are positioned in such a manner so as to be contacted by the longitudinally moving cam to effect ejection of the staples.
Each of the instruments described above were designed for use in open surgical procedures wherein surgeons have direct manual access to the operative site. However, in endoscopic or laparoscopic procedures, surgery is performed through a small incision or through narrow cannulae inserted through small entrance wounds in the skin. In order to address the specific needs of endoscopic and/or laparoscopic surgical procedures, an endoscopic surgical stapling apparatus has been developed and is disclosed in U.S. Pat. No. 5,040,715 to Green et al. This apparatus is well suited for such procedures and includes a fastener applying assembly having an anvil and a staple cartridge provided at the distal end of an endoscopic portion which permits the instrument to be inserted into a cannula and be remotely operated by the surgeon through manipulation of a proximal handle mechanism.
During the performance of a surgical stapling procedure, it is necessary for the surgeon to be well aware of the dimensional limitations of the instrument which they are using. For example, when tissue is to be stapled and cut, the surgeon must be able to accurately position the tissue within the jaws of the apparatus to ensure the tissue will be properly stapled and cut. In the past, markings have been imprinted on the cartridge carrying member of such stapling instruments. See, for example, U.S. Pat. Nos. 4,633,874, Des. 272,851, Des. 278,080 and Des. 284,698. However, during certain procedures, the instruments may be oriented in a position where the cartridge carrying member is blocked from the surgeon's view.
Accordingly, there is a need in the art for an anvil having graduations or markings provided thereon to delineate the dimensions of the instrument such as the boundaries of the staple forming area formed on the anvil, the range through which the knife blade travels to cut tissue, and/or the range through which the staple driving member travels to eject staples from the cartridge. The present invention describes both conventional and laparoscopic surgical stapling instruments having graduated anvils to serve these needs.